Pitot control system for aircraft



w. P. LEAR Dec. 12, 1944.

PITOT CONTROL SYSTEM FOR AIRCRAFT Original Filed Sept. 27, 1939 3 Sheets-Sheet 1- INVENTOR WM Rid mam ATTORNEY Dec.'12, 1944. w LEAR 2,364,637

PI'I'OT CONTROL SYSTEM FOR AIRCRAFT original Filed Sept. 27, 1959 3 Sheets-Sheet 2 5N 55 M15564. j H l I v 1 INVENTOR pwzzbwPiw BY MJM ATTORNEY Rm km .NuWNLH F 1944. w. P. LEAR PITOT CONTROL SYSTEM FOR AIRCRAFT Original Filed Sept. 27, 1939 3 Sheets-Sheet 5 W -lNVE;l.-9TOR BY M4 a ATTORNEY Patented Dec. 12, 1944 -1 PITOT CONTROL SYSTEM FOR AIRCRAFT William P. Lear, Dayton, Ohio, assignor, by mesne assignments, to Lear Avia, Inc., Piqua, Ohio, a

corporation of Illinois Original application September 27, 1939, Serial No.

296.725. now Patent No. 2.272.213. dated February 10, 1942.

Divided and this application March 16, 1940, Serial No. 324,263

16 Claims. (01. 250-43) ing application, entitled Antenna reeling system, which matured into Patent No. 2,272,213

on February 10, 1942, and is assigned to the same assignee as is the present case. The automatic.

velocity control arrangement has various applications, particularly aboard an aircraft. The

invention is herein specificall described in connection with the extension and retraction of a trailing wire on an aircraft.

The presence of an extended trailing antenna wire during landing and take-01f maneuvers of an aircraft is rather dangerous. It has heretofore been necessar at such times for the pilot to watch for and efiect retraction of the trailing wire. In accordance with the present invention, automatic means are provided, controlled by the velocity of the aircraft, to prevent the extension of the antenna wire prior to take-off or until the aircraft attains a safe predetermined Velocity. The invention is furthermore adapted to automatically retract any extended wire portion when the aircraft falls below the predetermined speed prior to landing. The pilot need not accordingly be concerned with dangerously dangling wires during low flight speed or altitude.

Mypresent invention contemplates an electrical switch in circuit with a reversibly operated motor, which switch is actuated in accordance with an air pressure condition developed by the aircraft in flight. Specifically, a Pitot tube arrangement is positioned.- exterior of the aircraft and coupled to the pressure actuated electrical switch. The system is adapted to initiate a retracting operation on the reeling mechanism when the speed of the aircraft falls below a predetermined value, such as '70 miles per hour. The switch is furthermore adapted to prevent operation of the reeling mechanism for extending the antenna while the aircraft speed is below the predetermined value.

present application is a division of my copend It is accordingly an object of my present invention to provide a novel method of and means for automatically controlling the operation of a mechanism upon a high-speed vehicle, in accordance withthe velocity of the vehicle.

Another object of the present invention is to provide novel arrangements for controlling a reversibly operable mechanism aboard an aircraft in accordance with the speed of the aircraft with respect to a predetermined value.

Still another object of the present invention is to provide a novel arrangement for operating a reversible mechanism in a predetermined manner when the speed of the aircraft on which the mechanism is mounted is below a predetermined amount.

A further object of the present invention is to provide a novel arrangement for automatically retracting an extended portion of a reelable antenna wire aboard an aircraft, when the velocity of the aircraft falls below a predetermined value.

Still a further object of the present invention is to providea novel system for automatically preventing the extension of an antenna wire by a reeling mechanism while the speed of the aircraft is below a predetermined value.

These and further objects of the present invention will become more apparent from the following description of a preferred embodiment thereof, taken in connection with the drawings, in which:

Fig. 1 is an assembly view of the components of a system in accordance with the present invention for controlling an antenna reeling mechanism installed aboard an aircraft.

Fig. 2 is a diagrammatic electrical and mechanical representation of details of the antenna reeling system corresponding to Fig. 1.

Fig. 3 is a horizontal cross-sectional View through the remote control unit taken along the line 3-3 of Fig. 1.

Fig. 4 is an end view of a roller contacting arrangement for the antenna wire, corresponding to the View seen along the line 4 l of Fig. 1.

Fig. 5 is a plan view of the antenna reeling mechanism employed in the illustrated system of the invention.

Fig. 6 is a cross-sectional view through the antenna reel and associated driving arrangement as taken'along thelin'e 66 of Fig. 5.

Fig. 7 is a vertical cross-sectional view through the retractable fair-lead and associated switching mechanism as taken along the line ll-l of Fig. 1.

An assembly of physical embodiment of the remotely controlled antenna reel of my invention is illustrated in Fig. l. The antenna wire is wound upon a reel l l of insulating material and extends through a guide-tube or fair-lead it. to a streamline fish or weight 13 attached to its end. Reel H is mechanically connected to the electric motor l4 through a reduction gear arrangement l5 mounted upon a unitar chassis construction [6. The motor i4 is electrically connected by cable I! to the remote control box I8 situated near the pilot. Battery cable [9 connects to a primary source of current on the aircraft. I prefer to use the standard direct current aircraft battery for operating motor [4 and the control circuits therefor. A flexible cable 20 mechanically connects the remote control box l3 to antenna reel H and the reduction gearing IS. A positive control of, as well as an indication for the length of antenna wire H) extended or retracted is made possible by flexible connection 20.

Chassis It supports the antenna reel and associated structure including motor M and reduction gearing 55 as a compact unitary mechanism. Chassis it is drilled with mounting holes for attachment thereof to the primary structure of the aircraft. The unit is preferably mounted with flared end section 2! projecting through tube l2, together with fish [3, extending through the fuselage of the aircraft as indicated by the belly line 22 of the aircraft. Antenna wire H1 is in continuous electrical connection with terminal post 23, connected to output terminal 24 of radio transmitter 25 by connection lead 25. It is to be understood that antenna I!) may be used for radio reception as well as for radio transmission.

The radio transmitter 25 is located adjacent the motor-reel unit which is located near belly line 22 of the aircraft. The radio transmitter 25 is remotely controlled or operated in a manner well known in the radio art so that it may be located remote from the control region of the plane. This arrangement permits a very short and direct connection 28 between the output of the transmitter 25 and the antenna reel Ill. The very short connection lead 25 permits negligible radiation of the antenna signal within the aircraft structure, since the radiation occurs along the conductor connected to the high potential radio frequency output of the transmitter 25. The location of the motor-reel unit near the point of the plane through which th antenna projects facilitates the reeling-in and reelingout operations and minimizes radio frequency energy losses.

The important advantages of my novel variable length trailing wire antenna system reside in that the pilot may adjust the trailing wire portion to obtain optimum transmission efficiency of the radio transmitter 25, and that the antenna reel l0 and projecting portions thereof are directly connected to the output terminal 24 of the radio transmitter 25 by a short connection 25 to prevent radiation losses internally in .the aircraft. The radio transmitter is preferably remotely controlled from the dashboard to which it is connected by the electrical cable indicated at 25. The remote control radio transmitter is operated by relays, not shown.

Although I prefer to operate the antenna reel ID by the automatically operated electrical motor system illustrated in the drawings, it is to be understood that manual operation of the reel from a manually operated reeling system is that the airplane pilot is relieved of any winding duties which the manual antenna reel system would entail. Other features of my present invention, while illustrated in connection with an electrically operated system, may also be derived in conjunction with a manually operated mechanical system.

A further important feature of my invention resides in providing an automatic safety switch 2'! for preventing unreeling of the trailing antenna it when the speed of the aircraft is less than a predetermined velocity, for example less than seventy miles per hour. Safety switch 21 is adapted to automatically actuate the motor for reeling-in and fully retracting the antenna ill at all times except when the speed of the is above the predetermined speed. Safety switch 2'! is suitably connected to the motor-reel circuit and responsive to an air-pressure created by the motion of the aircraft in flight. I prefer to obtain the air pressure from the Pitot tube which is standard equipment on airplanes in conjunction with instruments for measuring various conditions of flight. The safety switch 21 can be arranged to be responsive to a pressure greater than atmospheric for actuating the safety switch relay in a manner to be hereinafter described.

Safety switch 21 is connected to air pressure tube 28 which communicates with the standard Pitot tube 29 mounted upon the wing structure 30 of the aircraft. Pitot tube 29 may be located at any suitable portion of the aircraft. It is to be understood that the differential air pressure actuating the safety switch may be generated by other means than the Pitot tube. The pressure will vary in accordance with the velocity of the aircraft. Safety switch 21 is designed to respond to a pressure which corresponds to a pressure generated at the Pitot tube or other unit connected to the air tube 28 when the ship attains the predetermined minimum velocity, such as seventy miles per hour.

Remote control unit l8 contains a scale 3| calibrated in feet or length of antenna wire Ill extended from the reel I I. In operation, length control pointer 32 is manually turned to point to the number in feet corresponding to the length it is desired to extend antenna I0. By turning switch 33 into the out position, reel motor I4 will be energized to rotate in the direction to unreel antenna H1. The streamline weight or fish I3 will draw antenna 10 downwards and away from the ship in a manner well known in the art, giving a taut antenna structure. Flexible cable 20 is mechanically connected to control unit l8 in a manner to be described and cooperate with the setting of control pointer 32 for automatically stopping the operation of motor [4 when the pre-set length of antenna has been unreeled.

When switch 33 is turned to the in position, the electric motor 14 is connected to rotate in the proper sense to reel-in the extended antenna wire It). When the antenna wire is practically reeled in, weight [3 attached to the end portion thereof abuts bell-shaped end member 2|, and

actuates switch 34 to open the motor circuit and prevent further reeling-in. The switch 34 is the in-limit switch for preventing breakage of the antenna wire l and for automatically stopping the motor at the proper instant. I provide a further motor cut-off means at the control box unit for independently disconnecting motor l4 as a further precaution to prevent injury to the mechanism should weight I3 be broken off and unable to operate in-limit switch 34. Weight I3 is connected to the end of antenna ID by ballbearing swivel joint 35 insuring free rotation of the weight and prevent its twisting off. The streamline contour of the weight l3 minimizes its aerodynamic resistance in flight.

A flexible trailing wire 36 of fixed length extends beyond the fish or lead weight I 3, and is in continuous electrical contact with antenna wire l0 through the swivel joint connection 35. Flexible trailing wire or tail 36 is preferably six to ten feet in length, so as to project beneath the aircraft and notinterfere with landing or takeoff operations of the airplane; Tail 36 is suinciently long for efficient practical communication with the landing field during landing and take-off. After the plane has attained its normal flight speed, the proper length of antenna is extended depending upon the communication requirements, well known in the radio art.

Pilot lamps 3'! light up on remote controlunit l8 when trailing antenna wire I 0 is extended, and serve as a warning that the antenna is extended. The pilot lamps 31 are automatically cut-off when the antenna I 0 is comletely retracted as will become evident hereinafter.

Fig. 2 is a schematic diagram showing the preferred electrical and. mechanical connections corresponding to the antenna reel mechanism illustrated in Fig. 1. Remote control unit l8 comprises worm gear 40 driven by worm 4| which is mechanically connected to reduction gear unit by flexible cable 20. Gear 40 is rotated so as to correspond to the actual rotation of reel H and serves as a measure of the degree to which the reel H is extended. The gear 40 is illustrated in its normal position, corresponding to the fully retracted position of antenna ID as shown. In this position, an. insulation nib or projection 42 operates against cam switch 43 to maintain it open. A disk 44 is connected to gear 40. by means of a frictional coupling indicated at 45. Disk 44 is mechanically secured to control pointer 32. An insulated projection 46 is attached to disk 44 in a, predetermined position. for actuating cam switch 41.

Safety switch 21 comprises a housing 48 having a flange 49 at one end for mounting onto a suitable portion of the aircraft. A flexible diaphragm 50 is suitably supported within housing 48, and is preferably mounted to prevent air leakage around the diaphragm. The air pressure tube 28 communicating to Pitot tube 29 connects to one side of the air chamber formed by diaphragm 50 through opening 5| in flange 49. The pressure on the right side of diaphragm 50 of Fig. 2 depends upon that developed at Pitot tube 29 or other device for creating a pressure in accordance with the velocity of the aircraft as hereinabove referred to. The left air chamber within housing 48 communicates to atmospheric pressure by means of an opening to the atmosphere.

Relay contacts 52, 53 and '54 are mounted within safety switch structure 48 asv schematically indicated. Double contact 53 is supported cenprevent any unreeling of the antenna.

The unreeling or extending operation of the antenna wire H! can occur only when contacts 52 and 53 are connected in response to the air pressure developed on the right hand chamber in the safety switch 21 as communicated from the air pressure tube 28. It is to be understood that it is feasibl to operate on the vacuum side of the Pitot tube, or with a different pressure device wherein air pressure is developed in the righthand chamber deflecting diaphragm to ,the left and closing contact 53 upon contact 52. If a vacuum pressure is used for actuating switch 21, it is obvious that the relative position of contacts 52 and 54 will be reversed so that the deflection of the diaphragm to the right, in response to decreased pressure in the right-hand chamber will close the contacts of the circuit correspondin to 512 and 53.

In order to extend the antenna a predetermined length, the pointer 32 is turned opposite the figure on dial 3| (Fig. 1) corresponding to that length. Disk 44, being mechanically coupled with pointer 32, is angularly displaced therewith the same amount, moving projection 45 away from the cam switch 41 as shown in solid in Fig. 2. The dotted position 46a of the projection is the "cut-out position, for opening the motor circuit at cam switch 41 when the predetermined length of antenna It] has been unreeled or extended as will be hereinafter described. The displacement of projection 45 and pointer 32 shown in Fig. 2 represents about one-fifth of a revolution for disk 44 and corresponds to approximately one-fifth of the antenna to be extended. If, for example, the length of the extensible antenna is one hundred feet, such setting will correspond to about twenty feet as marked on dial 3| shown in Fig. 1. Cam switch 41 is permitted to close by the displacement of projection 46, and the out circuit is completed through relay 56 as follows:

A series circuit extends from switch 4'! through connection lead to'out relay 5B and ground. The other side of cam switch 41 is connected to in-out switch 33 through connection lead 51 and l continues from switch 33 through connection lead 58, through closed safety switch contacts 52, 53 back through connection lead 59 of Pitot switch cable 60 to the ungrounded terminal of battery 6|. Battery 6! is preferably the standard direct current battery of the airship, or any other suitable voltage source for actuating motor I 4 and the associated relay circuits. Summarizing, cam switch 4? is closed after pointer 32 is displaced to a reeling-out position, connecting battery 6| in series with out relay 56 when in-out switch 33 is connected to the out position, and when safety switch contacts 52, 53 are in contact under flight conditions.

When out relay 56 is energized, its armature circuits (i2 and 63 are closed and accordingly directly connect armature 64 and series field winding 65 of reel-motor I 4 across battery 6|. Motor- I4 is illustrated as a series motor which operates on directcurrent from battery 6!. The sense of rotation of motor l4 depends upon the relative connection of series field 65 with respect to armature 64as is'well known in the electrical art. Bypass condenser 66 is preferably connected across armature B4 to suppress high frequency currents which might be generated by motor commutation. When out relay 56 is energized, reel motor I4 is accordingly energized to rotate in the predetermined direction corresponding to the reel-out of antenna wire I0.

Armature 64 of motor I4 is directly coupled to reduction gearing l5 by coupling member indicated at 61 and drives reel I I at a predetermined. rate. When antenna I is let-out or unreeled, fish or weight I3 holds the wire taut. When Weight I3 is released from bell end 2| of slidable tube Hl, it permits spring 68 to draw tube 10 out and close contacts 34 of the in-limit switch.

When switch contacts 34 are closed, a circuit is completed through connection leads 1| and 12 to the signal or pilot lamps 31 which are connected in parallel, back through connection leads I3 and 11 and to battery 6 I. Switch 34 accordingly completes the pilot light circuit which flashes an indication on remote control unit l8 that some portion of the antenna is extended. When the antenna is retracted, weight I3 abuts flared end 2| of sleeve I0 against the action of the spring 58, and opens switch 34. The circuit to indicator lights 31 is then opened and the pilot is apprised that the antenna is fully retracted. By the term fully retracted I mean that the extensible portion of antenna I0 is substantially fully drawn in to the position as shown in the drawings. The tail or flexible appendage 36, useful for short distance communication, remains extended in the preferred design of the antenna reel mechanism. The opening of switch contacts 34 also open the circuit of motor I4 if it is still in circuit connection. When weight I3 moves against the flared sleeve 2| the antenna wire is prevented from snapping or breaking.

Antenna I0 is unreeled by positive motivation of motor I4 when the mechanism is connected to the out position. as shown in Fig. 2. The rotation of reel II correspondingly rotates worm 4| through flexible cable 20 and drives worm gear 40in a counter-clockwise direction. The rotation of worm gear 40 moves disk 44 counter clockwise due to the frictional coupling 45 therebe-- tween. Accordingly as antenna I0 is extended, projection 46 is rotated counter-clockwise back towards its original dotted position 46a.

When projection 46 reaches the position 48a, cam switch 41 is opened to disconnect motor I4 and discontinue the unreeling operation. The angular movement of gear 40 and disk 44 is preferably calibrated to correspond with the actual length of antenna extended during the reeling operation. The effect of projection 46 is to disconnect the motor circuit after disk 44 has rotated an amount corresponding to the calibrated displacement thereof, twenty feet in the present example. Projection 42 on worm gear 40 is moved to the dotted position 42a, electrically closing cam switch 43 to the dotted position 43a.

The reeling-in or retracting operation of the antenna I0 is accomplished by connecting switch 33 to the in contact. Cam switch 43, being closed in dotted position 43a, causes inrelay I5 to be energized since the following series circuit is completed: lead 16 to relay 15, to contacts 34 (which are closed when antenna I0 is extended), to ground, through battery 6|, to cable lead 11, back through connection lead 59, across safety switch contacts 52, 53 to the closed dotted position 33a of switch 33 through lead 58 and back to cam switch 43.

Energization of in-relay 15 attracts its armatures I8 and 19 to close the circuit of motor I4 through battery 6| to cause it to rotate in the opposie direction to that when armatures 62 and G3 are closed by the out relay. Reel II is accordingly rotated to retract antenna I0 until weight I3 abuts sleeve 10 at the flared end 2| and opens in-limit switch contacts 34. The in relay I5 is then immediately deenergized, opening the motor circuit.

During the retracting operation flexible cable 20 correspondingly rotates worm gear 40 in a clockwise direction, bringing projection 42 to its original position, shown in solid, to open cam switch 43. Opening of cam switch 43 by projection 42 may not occur simultaneously with the opening of the in-limit switch 34. However, switch 34 is the safety means for insuringproper opening of the reeling-in circuit since it is the positive indication of complete retraction of antenna I 0. Projection 42 serves as a check for opening the motor circuit in time should weight I3 be lost or otherwise fail to function, preventing continuous and high-speed reeling of the system at that time.

The frictional engagement between disk 44 and gear 40 moves projection 46 from position 46a, corresponding to an extended position of disk 44 when pointer 32 is displaced, back to its original position 46 when the antenna is fully retracted. To again extend the antenna to the same degree corresponding to the position of pointer 32, it is merely necessary to reconnect switch 33 to the out position. To extend the antenna a different amount, it is merely necessary to shift pointer 32 to the position opposite the length to be extended as marked on dial 3| and the apparatus will function to extend the wire the new amount. The reeling-out operation of the antenna system of the illustrated embodiment can occur only when safety switch 21 is actuated by a predetermined pressure in the air pressure tube 28 to close contacts 52, 53. Means may be provided to short-circuit the action of switch 21, or it may be eliminated.

Should the speed of the plane fall below the predetermined speed so that diaphragm 50 moves towards the right to open contacts 52, 53, any reeling-out operation becomes ineffective through the normal control at switch 33. Relay contacts 53, 54 are closed when the speed of the plane is sufficiently reduced, closing the retracting or reeling-in circuit through leads 59 and 80, by short-circuiting in-out switch 33 to the in position. The effect of the reduced speed of the aircraft is to automatically throw in-relay 15 into circuit since cam switch 43 will be normally closed to position 43a if any of the antenna I0 is extended. Energization of relay 15 operates motor I4 to rotate reel II to retract antenna III until weight I3 abuts sleeve 10 and opens in-limit switch 34. The motor circuit is then immediately disconnected from battery BI and the antenna is safely retracted for landing operations of the plane. The warning lamps 31 are continuously in circuit and light up while antenna Ill is extended to any degree and in-limit switch is closed.

Fig. 3 is a cross-sectional view taken horizontally through remote control unit I8 along line 33 of Fig. 1. The housing BI is cast to contain a boss 82 for supporting worm 4!, and a bearing 84 for supporting control disk 44 and worm gear 40. A back plate 83 is screwed onto housing 8| and may contain holesfor mounting theunit l8 onto the aircraft structure. Worm 4| meshes with the worm gear 40. Worm gear 40 is attached to sleeve 85 coaxial about rod 86. Sleeve 85 is closely fitted about rod 86 to form a frictional engagement therewith. Dial 3| is peened onto a shoulder at the end of sleeve 85 and accordingly rotates directly with gear 40. The selective length control pointer is secured to knob 86 which is manually operated in the manner already described.

Pointer 32 and knob 81 are mechanically connected to control disk 44 by means of central rod 86; knob 81 being peened onto the rod 86, and disk 44 secured to rod 86 by set-screw 89. A spring 90 concentric with rod 86 and located within a cavity in knob Bl mechanically biases disk 44 against a spacer or composition washer 9| towards worm gear 40. Disk 44 is accordingly frictionally engaged with worm gear 40 and is rotated therewith. The positive engagement of gear 40 with worm gear 4| permits disk 44 and knob 81 to be manually displaced independently of the worm gear 40 and to perform the selective length control functions hereinabove described in connection with diagrammatic Fig. 2.

Fig. 4 is an end view of the continuous antenna contact means as viewed from the line 4-4 in Fig. 1. Guide-tube I2 is shown supported on an insulation block |04 by strap 93. Block I04 is attached to the common chassis IS. The edges of thassis I6 are curled over to stiifen and strengthen the chassis. Antenna wire I is in continuous electrical and frictional contact with the tubular rollers ||0 spaced by a distance equal to the diameter of the wire l0. Rollers ||0 are supported by metallic brackets HI and H2 and are electrically interconnected therewith. A terminal post 23 is connected to the top bracket H2. The wire 26 connecting to radio transmitter 25, as shown in Fig. 1, is accordingly conductively connected to the antenna wire l0 as will now be evident. Continuous electrical contact is maintained for the variable lengths of the extended antenna. There is no danger of short-circuiting antenna 10 to ground since should it be displaced from the central position it could only touch upon insulation guide-tube l2. By leading antenna wire N at an angle to "the central position of the Wire in tube l2, in a manner illustrated in Fig. 5, in-

creased frictional contact occurs at one of the rollers I I0.

Fig. is a plan view of the motor-reel assembly as a unitary structure with chassis I0. Chassis |E is preferably of metallic material and contains mounting brackets 92 and 93 for securing the fairlead or sleeve |2 in position. Movable or retractible sleeve is slidable within sleeve |2 and contains flared end 2|. Sleeves l0 and I2 are made of insulation material such as Bakelite or composition to prevent short-circuiting of antenna wire |0 to ground through chassis l6. Flared end 2| is preferably of metallic construction, such as steel, to resist shock and wear resulting from impacts by the weight l3. Reel l is rotatably supported on rod 94 adjacent the right end of the sleeve structure |2. Motor 4| is secured to chassis I6 at the extreme right end, cooperating with the reduction gear structure (not seen in Fig. 5). Remotely controlled relays 56 and are enclosed in housing 30.

The preferred physical cooperation between reel II and reduction gearing I5 is illustrated in crosssectional view Fig. 6, taken along the line 6--6 of Fig. 5. The shaft of motor I4 is coupled to worm 95 within reduction gearing unit I5. A worm gear 96 meshes with Worm 95 and is keyed to shaft 94 secured to reel structure Flexible cable 20 is mechanically coupled to shaft 94 by female coupling member 97 containing a socket cooperating with projection 98 of shaft 94. Flexible cable 20 and its connecting head 91 is maintained in position by sleeve 99 set into extension I00 of reduction gearing l5. Antenna reel comprises parallel disks I0 I, |02 of insulation material suitably spaced to contain antenna wire l0 therebetween. The antenna is insulated from the metallic structure of the motor drive as well as the supporting structure.

Fig. 7 is a cross-sectional view illustrating one embodiment of the in-limit switch and associated actuation arrangement as taken along the .line of Fig. 5. Outer tubular sleeve l2 is fixedly supported upon chassis l6 by straps 92, 93 and insulation blocks )3, H14. Movable sleeve i0 is slidably mounted within sleeve 12. Flared metallicmember 2| is secured to the outer end of slidable tube 10. A block N is attached to a portion of slidable tube 10 for actuating extended arm I06 of in-limit switch 34.

To facilitate mounting of block Hi5 on tube 10, I provide a slot 4 in tube 10 located directly above the position of block I05, and a further cor responding slot H5 in outer tube l2. When retractible tube l0 is in the extended position corresponding to that shown in Fig. 5, both slots I14 and H5 are lined-up and permit the insertion of a screw driver or other suitable tool for mounting block I05. Simple holes may be substituted for the slots H4, H5. Outer slot M5 on tube I2 is covered over a plate Hi5, such as a name plate, to prevent foreign matter from entering the assembly.

Block I05 accordingly is slidable with tube 20 and projects through a slot Hill on the bottom portion of the fixed sleeve l2. Spring 68 mechanically biases block I05 towards the left and with it slidable tube l0 as well. The normal position of tube 10 is the extended one as shown in Fig. 5, holding switch block Hi5 against the left end of the slot I06, away from arm I05 of switch 34.

When antenna i0 is fully retracted, weight I3 is drawn against the open end of the end member 2|, forcing tube T0 inwards against spring 68 and operating block )5 to the position illustrated in Fig. 7. Blade [06' is pressed downwards, opening the contacts of in-limit switch 34. Conversely, when antenna W is extended, spring 68 moves block 105 away from switch I06, effecting a closure of the contacts of switch 34. Pilot lights 3'! are then lit up, and the reeling operation disclosed in connection with Figs. 1 and 2 is permitted to take place. Antenna I0 is in continuous contact with rollers 0 connecting with the radio transmitter 25 by the short connection lead 26 are hereinabove described in connection with Fig. 1. n

An important advantage of the spring biased retractible tube 10 is that antenna wire I0 is kept taut when the antenna is completely retracted and the motor is disconnected when holding weight l3 firmly against flared end 2|. In practice, tube 10 is made retractible to the extent of several inches. Reel II is prevented from unwinding when motor I4 is not operating, due to the mechanical interlocking of worm gear with worm 95, as shown in Fig. 6. With weight l3 against flared end 2|, tube 10 is forced inwards against spring 68, maintaining antenna |0 taut after the motor circuit is disconnected. The

practical advantages resulting are that weight [3 is prevented from vibrating or chattering against nearby objects when the antenna is retracted, and a firm electrical connection between the tail 36 and the radio transmitter effected. Antenna tail 36 remains extended for local radio communication.

The safety switch 21 has been illustrated in electrical connection with the motor control circuit of an antenna reeling system to prevent ex tension of the antenna wire l before the aircraft reaches a predetermined velocity, and to automatically retract the antenna should any of it be extended while the aircraft flies below a predetermined speed. It is to be understood that the velocity operated switch corresponding to switch 21, in association with the velocity responsive pressure generating device corresponding to Pitot tube 29, may be employed with other electrically operated mechanisms aboard an aircraft or other high velocity vehicle. The velocity switch is continually effective, relieving the pilot of any concern as to the dangerous extension of an dangling antenna wire, or other required function to be performed when the aircraft is below the predetermined speed, independently of the condition of operation which the pilot may exert on the mechanism.

Although I have described a preferred embodiment for carrying out my present invention, it is to be understood that modifications may be made therein falling within the broader spirit and scope thereof as expressed in the appended claims.

What I claim is: I

1. The combination with a high-speed vehicle of mechanism for extending and retracting an antenna wire from said vehicle in desired lengths independent of the vehicle velocity and means responsive to the velocity of the vehicle and arranged for operating said mechanism to retract extended antenna wire when said velocity falls below a predetermined value.

2. An antenna system for a high-speed vehicle comprising a reel containing an antenna wire, mechanism for operating said reel to extend said wire from said vehicle in desired lengths independent of the Velocity of the vehicle, and means responsive to the velocity of the vehicle for preventing said mechanism from operating said reel to extend said wire when said velocity is below a predetermined amount.

3. An antenna system for an aircraft comprising a reel containing an antenna wire, mechanism for operating said reel to extend said wire outside the aircraft for predetermined lengths which are independent of the velocity of the aircraft, and means responsive to the velocity of the aircraft for preventing said mechanism from operating said reel to extend said wire when said velocity is below a predetermined amount.

4. An antenna system for a high-speed vehicle comprising a reel containing an antenna wire, mechanism for operating said reel to extend said wire from said vehicle in desired lengths independent of the velocity of the vehicle, and means responsive to the velocity of the vehicle for automatically causing said mechanism to operate said reel to retract any extended wire portion when said velocity falls below a predetermined amount.

5. An antenna system for a high-speed vehicle comprising a reel containing an antenna wire, a drag unit on the free end of said wire for projecting the wire outside the vehicle, mechanism for operating said reel to extend desired lengths of said wire from the vehicle, and means responsive to the velocity of the vehicle for automatically causing said mechanism to operate said reel to retract any extended wire portion when said velocity falls below a predetermined amount.

6. An antenna system for an aircraft comprising a reel containing an antenna wire, mechanism for operating said reel to extend and retract said wire in desired lengths independent of the velocity of the aircraft, and means responsive to the velocity of the aircraft for preventing said mechanism from operating said reel to extend said wire and automatically causing said mechanism to operate said reel to retract any extended wire portion when said velocity is below apredetermined amount.

7. An antenna system for an aircraft comprising a reel containing an antenna wire, a reversible electrical motor for operating said reel to extend and retract variable lengths of said, wire outside said vehicle, and means responsive to the velocity of the aircraft for preventing said motor from operating said reel until the velocity of said aircraft reaches a predetermined amount comprising Pitot means, an electrical switch actuated by. air pressure generated by said Pitot means, and means including circuit connections between said electrical switch and said reversible electric motor.

8. An antenna system for an aircraft comprising a reel containing an antenna wire one end of which projectsoutside the aircraft, a weight on the projecting end of said wire, a reversible electrical motor for operating said reel to extend and retract said wire independently of the velocity of the aircraft, and means responsive to the velocity of the aircraft for preventing said motor from operating said reel to extend said wire and automaticall causing said motor to operate said reel to retract any extended wire portion when said velocity is below a predetermined amount comprising Pitot means exterior of the aircraft for generating an air pressure in accordance with the velocity of said aircraft, a chamber, a diaphragm mounted in said chamber, a tube connecting said Pitot means with said chamber for communicating the generated pressure to said diaphragm, and electrical contact means in circuit with said reversible motor and actuated by said diaphragm when said generated pressure reaches the predetermined amount corresponding to said predetermined aircraft velocity.

9. An antenna assembly for airplanes comprising an antenna wire, a reel to which one end of the wire is connected, a drag device at the free end of the wire, guiding means for the wire mounted on the fuselage of the ship at positions spaced apart, and means for rotating the reel to either reel out or reel in the wire between its minimum and maximum effective lengths, said means comprising a reversible motor, irreversible driving means through which the motor turns the reel selectively in either direction, alternative circuits for the motor for causing the motor to rotate in either direction, a manually operable control switch for selectively closing or opening either circuit whereby the antenna may be adjusted to and held at any desired length between its maximum and minimum effective lengths, a normally open switch in the reeling-out circuit, and wind-pressure operated means independent of the antenna for closing said switch when the ship is in flight.

10. In combination with an antenna for an airplane, means for supporting the antenna from the airplane, means for reeling in or out this antenna and holding it at minimum, maximum or intermediate effective lengths comprising a reversible motor, and alternative reeling in and reeling out circuits for energizing the motor, means for automatically opening the reeling out circuit when the antenna is extended to its maximum length, means for automatically opening the reeling in circuit when the antenna is drawn in to its minimum efiective length, means for automatically opening the reeling out circuit when the airplane is not in motion, and a manually operable switch effective to alternatively open or close either circuit at any time except when said circuit is broken by one of said automatic means.

11. In combination with an antenna for airplanes, a reel on which a portion of the antenna may be wound and from which the antenna may be reeled out when the ship is in flight, a motormechanism-for rotating the reel, a circuit for actuating the motor-mechanism to reel-out the antenna, a manually operable switch for closing this circuit, a self-opening switch in this circuit, and air-pressure operated means independent of the antenna for automatically closing this latter switch when the ship is in flight.

12. In combination with electrically actuated antenna-operating equipment on an airplane, including an actuating circuit, a manually operable control switch for said circuit, a self-opening switch in said circuit, and wind-pressure operated means independent of the antenna for automatically closing this latter switch when the ship is in flight.

13. In combination with electrically actuated antenna-operating equipment on an airplane, means for controlling said equipment while the airplane is in flight, a switch movable normally to a position which renders said equipment inoperative by said control means, and air-pressure operated means independent of the antenna for moving said switch, when the airplane is in flight, to render said equipment operative by said control means.

14. An antenna system for an aircraft comprising a reel containing an antenna wire one end of which projects outside the aircraft; a reversible electric motor for operating said reel; mechanism settable to preselect the amount of extension and retraction of said antenna wire relative to the aircraft; a first circuit for energizing said motor for operation in a direction to extend said antenna wire, including a manually operable switch, a normally closed switch opened by said mechanism when said antenna wire is extended the preselected amount, an air pressure responsive switch operative when the velocity of the aircraft is below a predetermined amount to render said first circuit ineiTective to energize said motor, and circuit means connecting said switches in series circuit relation to said motor and a source of power; and a second circuit for energizing said motor for operation in a direction to retract said antenna wire.

15. An antenna system for an aircraft comprising a reel containing an antenna wire one end of which projects outside the aircraft; a reversible electric motor for operating said reel; mechanism settable to preselect the amount of extension and retraction of said antenna wire relative to the aircraft; a first circuit for energizing said motor for operation in a direction to extend said antenna wire; a second circuit for energizing said motor for operation in a direction to retract said antenna wire, including a manually operable switch, a first normally closed switch opened by said mechanism when said antenna wire is retracted the preselected amount, a second normally closed switch, circuit means connecting said switches in series circuit relation to said motor and a source of power, and an air pressure responsive switch operative when the velocity of the aircraft is below a predetermined amount to shunt said manually operable switch to close said second conduit; and means operable by said antenna wire then fully retracted to open said second normally closed switch.

1o. An antenna system for an aircraft comprising a reel containing an antenna wire one end of which projects outside the aircraft; a reversible electric motor for operating said reel; mechanism settable to preselect the amount of extensionand retraction of said antenna wire relative to the aircraft; a first circuit for 81'181' gizing said motor for operation in a direction to extend said antenna wire, including a manually operable switch, a normally closed switch opened by said mechanism when said antenna wire is extended the preselected amount, an air pressure responsive switch operative when the velocity of the aircraft is below a predetermined amount to render said first circuit ineffective to energize said motor, and circuit means connecting said switches in series circuit relation to said motor and a source of power; a second circuit for energizing said motor for operation in a direction to retract said antenna wire, including a second manually operable switch, a second normally closed switch, opened by said mechanism when said antenna wire is retracted the preselected amount, a third normally closed switch, circuit means connecting said switches in series circuit relation to said motor and the source of power and said pressure responsive switch; said pressure responsive switch being operative when the velocity of the aircraft is below such predetermined amount to shunt said second manually operable switch to close said second circuit; and means operable by said antenna wire when fully retracted to open said third normally closed switch.

WILLIAM P. LEAR. 

